1. Field of the Invention
The invention relates to a method for the determination of optimum parameters for a casting process, particularly on die-casting machines or the like, known data sets of individual parameters of a casting cycle being available.
2. Description of the Related Art
Automatic monitoring of the casting process during die-casting is known from the literature reference Gie.beta.erei 68 (1981) No. 18, Page 531 ff.) and this system employs the fundamental method of die-casting control. Hitherto known monitoring systems for casting processes are based on a comparison of measured actual values for a very wide variety of parameters with predetermined desired values while the casting process is running and on the performance, if required, of corrections in the same or the subsequent casting cycle in order to match the actual value curve, for example, to the desired value curve.
In another method, described in DE 31 11 425 C2, a plurality of successive values for a particular operating parameter are stored in a first learning phase during an operating sequence of a machine tool and, taking account of permissible tolerance deviations, these values are used in the formation of limiting values. In a subsequent monitoring phase, it is determined whether the values for this operating parameter which then occur undershoot or exceed these limiting values. In the formation of the limiting value for the monitoring phase, use is made either of the maximum value or the minimum value or of an average value for the values stored in the learning phase. The aim of this known teaching is to shut down a machine tool if, during the operation of the machine, an operating parameter exceeds or undershoots the limiting value determined in this way.
In the control of machines and, in particular, die-casting machines, the recording and storage of process parameters and the formation of reference values with tolerance intervals is accordingly known. Thus, for example, DE 36 22 822 C2 describes a method for the control of a machine with corresponding control values, the operating conditions of the machine being recorded, control parameters stored and the control values using which the machine is controlled determined on the basis of the operating conditions recorded.
In practice, wide-ranging tests are carried out to allow the interdependence of a plurality of parameters, the settings of which have an effect in the operation of a production plant on the quality of an end product, to be mastered in terms of control. Particularly in the case of die casting, there is an extremely large number of such parameters, such as, for example, the melting temperature, the metered quantity, the acceleration or speed during the various phases of the casting process, the force applied to the casting plunger rod, the position of the changeover point between the individual phases, the accumulator pressure at the beginning of the second phase, the position of the plunger at the changeover point, the die temperatures, the ejector force, the lubricant quantity per nozzle, the injection times, the composition of the melt, etc. Some of these parameters are also mentioned in the publication "Gie.beta.erei . . . " mentioned at the outset.
The correlations between such variables themselves and between them and the quality of the parts produced are so complex that an undesirably high proportion of reject parts may be produced even in the most modern plants.
In another known method for monitoring injection molding processes in the production of plastic parts in accordance with EP 0 126 722 B1, parameter values in the production process are used as reference data for the formation of a reference curve shape for those products produced which are defined as molded articles of a quality which is still good. In this method too the measured actual data are then compared in subsequent series production with the predetermined reference data of the parameter value, tolerance limits determining the permissible deviations.